Load handling in fork-lift trucks movable fork cover for forklift truck

ABSTRACT

In a forklift truck, at least one, and preferably both, of the horizontal load-supporting tines, which extend forward in cantilever fashion from a vertically movable fork apron, are provided with load-engaging cover members which are selectively movable along the lengthwise of the tines. The cover members are movable independently of each other along their respective forks so that the angular relationship of a load supported on the forks may be adjusted relative to the length of the truck about an axis passing vertically through the load, thereby making it possible to precisely adjust the position of a load supported by the truck relative to a foundation upon which the load is to be supported without moving the truck per se.

United States Patent Primary Examiner-Gerald M. Forlenza AssistantExaminer-Raymond B. Johnson Attorney-Christie, Parker & l-lale ABSTRACT:In a forklift truck, at least one, and preferably both, of thehorizontal load-supporting tines, which extend forward in cantileverfashion from a vertically movable fork apron, are provided withload-engaging cover members which are selectively movable along thelengthwise of the tines. The cover members are movable independently ofeach other along their respective forks so that the angular relationshipof a load supported on the forks may be adjusted relative to the lengthof the truck about an axis passing vertically through the load, therebymaking it possible to precisely adjust the position of a load supportedby the truck relative to a foundation upon which the load is to besupported without moving the truck per se.

PATENTEUFEB 919?: 3561628 SHEET 2 0F 2 INVENTOR.

This application is a continuation of my copending application Ser. No.426,482 filed Jan. 15, I965, for Load Handling In Forklift Trucks, whichapplication (now abandoned) was a continuation-in-part of applicationSer. No. 401 ,413 filed Oct. 5, 1964, now abandoned, bearing the sametitle.

In using forklift trucks to stack articles for storage and the like, itis often very desirable, and in many cases necessary, that the articlebe deposited by the truck in substantially perfect angular alignmentwith the upper end of a partially complete stack or with a foundationfor a stack. This is true whether or not the article is supported on apallet which, in turn, is supported on the spaced forks of the forklifttruck.

For example, in sawmills green lumber is arranged in unit stacks whichusually are of considerable length. Several of these unit stacks arearranged vertically for drying of the lumber contained therein. Forklifttrucks are used to compose the large stacks. Since the large stacksoften become quite high, it is necessary, for the stack to be stable,that each unit stack be angularly aligned with the unit stackimmediately below it, and that the lowermost unit stack be properlypositioned on the foundation provided for it.

It is difficult, because of human errors in judgment, to properlyposition a lift truck adjacent a stack foundation so that a unit stackof lumber carried by the truck may be deposited properly on thefoundation. Usually the truck operator positions the truck adjacent thecenter of the foundation only to find that the elongate extent of thetruck load is skew to the elongate extent of the foundation. The truckoperator thus must yo-yo, i.e., back and turn, the truck to align theload with the foundation. As a result, the proper stacking of lumber isa difficult, time consuming and uneconomical process.

It is a simple matter, on the other hand, for an operator to position aforklift truck so that a stack of lumber carried by the truck ismisaligned in a given direction with a foundation for the stack. Thisinvention relies upon this fact and provides apparatus whereby thismisalignment may be corrected. The truck operator positions the truckadjacent the midlength of the foundation, and usually there is somemisalignment of the load with the foundation. He then operates theapparatus to shift the position of the load (the stack carried by thetruck) relative to the truck to align the load with the foundation. Theload is then deposited on the foundation.

Accordingly, in general terms, this invention provides apparatus whichis attachable to a forklift truck. The truck conventionally has avertically movable fork apron to which are mounted a pair of spaced forkmembers adapted to support a load. The inventive apparatus comprises anelongated cover member for one of the fork members. Means are providedfor mounting the cover member to the one fork member so that the covermember is adapted to engage and carry the load and so that the covermember is movable along the fork member toward and away from the forkapron. The apparatus further includes selectively operable means carriedby the cover member and adapted to be connected to the fork apron. Theselectively operable means is operable for moving the cover member alongthe one fork member.

The cover member is 'not a mere extension device for the fork member.Rather it is a load-carrying and load-driving member. The truck ispositioned adjacent the foundation for the load so that, in thepreferred case, the end of the load carried by the cover member isfarther out of alignment with the foundation than the other end of theload. The cover member is then moved toward the foundation to move theload on the fork members. The cover member is moved sufficiently toalign the elongate extent of the load with the length of the foundation.If desired, the truck can be moved closer to the foundation to positionthe load directly over the foundation. The load is then lowered onto thefoundation.

Only one of the pair of fork members need be provided with a covermember for the successful practice of this invention.

This is true since the direction of the error of alignment of the truckrelative to the load foundation is easily controlled by the truckoperator. Moreover, the extent of this error, between limits, is easilycontrolled by the truck operator. Accordingly, in the large majority ofsituations only one cover member is needed. The invention is describedbelow, however, as including a cover member for each fork member inorder to be complete.

The above mentioned and other features of the invention are more fullyset forth in the following detailed description of the invention takenin conjunction with the accompanying drawings wherein:

FIG. 1 is a top plan view of apparatus according to this inventionmounted to the front end of the forklift truck;

FIG. 2 is an enlarged perspective view with parts broken away of a forkmember fitted with apparatus according to this invention;

FIG. 3 is a side elevation view showing the connection of a fork memberto the fork apron of the truck;

FIG. 4 is a perspective view, similar to FIG. 2, of a fork member fittedwith another apparatus according to this inven tion; and

FIG. 5 is a side elevation view of the apparatus shown in FIG. 4.

FIG. 1 shows an industrial forklift truck 10 having a chassis II towhich are mounted front wheels I2. A vertical elevator 13 is mounted tothe truck chassis between the front wheels. The elevator includes a pairof C-shaped structural channels 14 which open toward each other todefine elevator tracks. The channels are disposed parallel to oneanother and are extended vertically from a support plate 15 movablymounted to the front end of the truck.

A fork apron 16 is mounted to the elevator for movement along thetracks. The fork apron includes a vertically oriented planar frame 17disposed transversely of the truck. A fork apron carriage 18 is securedto the rear central portion of frame 17 and carries a plurality ofwheels 19 on opposite sides of the carriage. The wheels are engagedbetween the flanges of the channels to movably engage of the carriagewith the elevator. An extensible hydraulic ram 20 is connected betweencarriage I8 and channel support plate 15 and is operable to move thecarriage vertically in the elevator tracks.

FIGS. 1 and 3 show a pair of fork members 21 connected to the fork apronon opposite sides of the elevator. Each fork member is a right angled,elongated forged member which has a vertically extending leg 22 and ahorizontally extending leg 23. The upper end of leg 22 is connected to asupport pin 24 carried by the fork apron frame. Leg 23 extends forwardlyfrom the front face the fork apron adjacent the lower edge of the frame.A bearing plate 25 is secured to the lower front surface of frame 17 andbears against the lower rear surface of fork member leg 22.

Each fork member 21 is a common type of fork member occurring in atypical industrial forklift truck. Fork member 21 is shown merely forthe purposes of example. It is within the scope of this invention thatthe structure of the fork member may vary from that shown and described.Preferably, however, the vertical thickness of the horizontal portion ofthe fork member decreases progressing forwardly of the fork from thestructure to which it is connected, as shown in FIG. 3.

An elongated cover plate 30, shows in FIGS. 1 and 2, is disposedadjacent the upper surface of each fork member. Preferably each plate 30has a width greater than the horizontal width of fork member leg 23 andhas a length less than the length of the leg. A flange 31 (see FIG. 2)depends from each longitudinal side of each cover plate along the lengthof the plate. The opposing surfaces of the flanges on each cover plateare spaced apart a distance greater than the width of the fork member.An inturned lip 32 extends from the lower extremity of each flangetoward the opposite flange of the cover plate. As shown in FIG. 2, theupper surfaces of the lips are spaced from the lower surface of thecover plate a distance greater than the thickness of the fork member.The cover plate is thus configured to be slipped longitudinally over thefork member and to be retained thereon by lips 32 and flanges 31.

Each cover plate is mounted to its fork member for movement along thefork member toward and away from the fork apron. As shown in FIG. 2, aroller bearing cage plate 35 is disposed between each cover plate andthe adjacent fork member. Preferably, the cage plate has a lengthsubstantially equal to the length of the cover plate. A plurality ofroller bearings 36 are mounted in each cage plate at locations spacedalong the cage plate. The roller bearings are disposed transversely ofthe fork member and extend above the upper surface of the cage plate toengage the underside of cover plate 30. The bearings and cage platesmount each cover plate to its fork member so that the weight of a loadengaged with the cover plates is transferred to the fork members.Moreover, they assure that the loaded cover plates are movable along thefork member.

The attachment apparatus provided by this invention also includesselectively operable means for moving each cover plate along its forkmember. As shown in FIGS. 1 and 2, a double-acting hydraulic ramassembly 40, having a cylinder 41 and a piston 42, is carried by eachcover plate. A bracket 43 extends laterally from that cover plate flangewhich, when the cover plate is engaged with its fork member, is disposedopp site from elevator 13. Each bracket carries a vertical plate 44which opens to the rear end, i.e., the apron end, of the cover plate towhich it is connected. The cylinder of a respective ram assembly isconnected to plate 44 and extends from the plate toward the fork apron.The ram assembly is aligned parallel to the elongate extent of the coverplate. The ram piston carries a lug 45 adapted to be connected to acooperating lug 46 carried by the fork apron adjacent the rear end ofthe horizontal portion of the fork member. It will be understood,however, that lug 46 may be connected to the fork if desired, as whenthe forks are movably laterally relative to the apron. it is preferredthat the ram assemblies be disposed below a horizontal plane defined bythe upper surfaces of cover plates 30 so that no portion of the weightof a load placed on the cover plates is borne by the ram assemblies.

Each ram assembly 40 is operable independently of the other ram assemblyto move its cover member along the adjacent fork member. Each covermember is guided in such motion by flanges 31.

Ram assemblies 40, described above, are exemplary of means which areprovided to move the cover plates along their cooperating fork members.The invention, however, is not restricted to the use of such devices.For example, a motor driven jackscrew may be connected between eachcover plate and the adjacent end of the fork apron. It is required onlythat whatever device which is provided for moving the cover plate alongthe fork member be operable independently of the mechanism provided forso moving the other cover plate.

As indicated above, the present invention is useful in positioning aload accurately in a preselected position even when the forklift truckwhich carries the load is located adjacent this position but is somewhatout of alignment therewith. The area enclosed in FIG. l by dashed linerepresents a preselected position in which a load, represented byphantom lines 52 and carried by truck 10, is to be deposited. The truckis disposed so that the longitudinal axis of the truck is slightly skewto the elongate extent of position 50. The load is disposed on the coverplates so that its midlength is centered between the cover plates. Thecover plates are positioned immediately adjacent the fork apron.

Points 54 and 55 represent the centers of pressure of the load upon theright and left cover plates, respectively, assuming a uniformdistribution of the load on each of cover plates 3%. I

To properly deposit the load in position St), the left end of the load(as viewed by the operator of the truck) must be moved forwardly of forkapron ll. Accordingly, the operator of truck l0 actuates ram assembly 40associated with the cover plate engaged with the left fork of the truckto move the cover plate (and center of pressure 55) forwardly along thecover plate a distance B, the chord by an arc A swung about point 54.Such operation of the ram assembly drives the load into alignment withposition 50 as the load pivots about the centers of pressure of the loadon the respective cover plates. The operator then need only lower thefork apron relative to the truck chassis to deposit the load in properalignment with position 50.

By providing each cover plate with a separate selectively operable meansfor moving the cover plate along its associated fork member, a forklifttruck equipped with this invention has the capacity to pivot a load ineither a clockwise or counterclockwise direction. As indicated above,however, the direction and extent of misalignment of the initialposition of the load relative to the position in which the load is to bedeposited is easily controllable by the operator of the truck. Forexample, the operator can position the truck so that the left end of theload is away from the foundation so that the error of alignment is from7% to 15 and requires a clockwise movement of the load relative to thetruck to align the load with the foundation. This error can bereproduced at will. Accordingly, a cover member need by provided only onthe left fork member for the practice of this invention.

FIGS. 4 and 5 show a second cover member 60 according to this invention.Cover member 60 is fabricated of heavy gauge sheet metal arranged toform a sheath which encloses the horizontal leg 23 of a fork member 21.The cover member has a closed end 61 for enclosing the toe of the fork,i.e., the end of the fork spaced from fork apron 16. The cover memberhas a lower surface which curves upward to the front end of the covermember; this curvature facilitates insertion of the fork and covermember under a load and also assures that the fork can be withdrawn fromunder a load without damaging either the cover member or the structureon which the load is deposited. The length of the cover member is suchthat a rear end 62 of the cover member is spaced from the vertical legof the fork when ram 4-0 is disposed in the midposition of its operatingrange; this is the normal or at rest position of the ram. A rollerbearing cage plate 35 is mounted inside the cover member between it andthe upper surface of the fork.

A skeg 65 is welded to the underside of the fork at the heel of the forkand is spaced from the end of the cover member, when ram 40 is in itsnormal position, by an amount equal to one-half the travel of piston 42.The skeg has a lower surface 66 curved convexly downward and faired intothe curvature of the heel of the fork. The skeg provides a stop for thecover member and also enables the fork to be withdrawn from under aload, after a load has been deposited, by sliding easily over whateverstructure the load is placed on.

Cover member 60 has sidewalls 68 which have extensions 69 extended tothe rear of the vertical leg of fork as shown in FIGS. 4 and 5. Theextensions have upper edges 70 which lie substantially in the plane ofthe top of the cover member. The extensions are particularly usefulwhere the load handled by truck 10 is lumber. In the absence of theextensions and with the cover member in its normal position, it ispossible for a piece of lumber from the load to drop into the spacebetween the rear end of the cover member and the front surface of forkleg 22. When this happens the cover member cannot be moved toward thefork apron without crushing the piece of lumber, nor can the fork bewithdrawn from under the load without taking the piece of lumber withit. The extensions, however, prevent a piece of lumber from falling intothe space between the rear of the cover member and the front face of thefork leg 22, thereby preventing these problems from arismg.

Lug 45 to which ram piston 42 is connected is notched as at '72 toreceive the adjacent cover member sidewall extension.

The structural strength of cover member 6th is provided in its top,bottom and sidewalls. Borrowing a phrase from the aeronautical industry,the cover member is skin stressed." The cover member is sufficientlystrong that it can receive a load within the capacity of truck l0 and bemoved in response to operation of ram 49 to move a load as describedabove.

it is a feature of the apparatus described above that the longitudinaldimension of a forklift truck is not increased by the addition of theapparatus to the truck, and the apparatus is light in weight.Accordingly, the load carrying capacity of the truck is not reduced.Moreover, operation of the apparatus does not produce any substantialshift in the center of gravity of a load carried by the truck. There issubstantially no lateral shifting of the center of gravity of the loadsince the center of gravity of the load moves along a line which extendslongitudinally of the vehicle. Accordingly, lateral stability of thevehicle is not impaired. Moreover, as shown above, this longitudinalshift in the center of gravity of the load relative to the truck issmall. There is substantially only rotational movement of the loadrelative to the truck chassis rather than rotational and translatorymotion. Accordingly, the truck operator need concern himself only withpositioning the truck at the desired location lengthwise of the positionin which the load is to be deposited; he need not worry about lateralshifting of the load as the angular relation of the load relative to theposition is adjusted.

It is a further feature of this invention that an existing forklifttruck can readily be equipped with the inventive apparatus. All that isrequired is to slip a cover plate or cover member in accord with theabove description over one of the forks of the truck and to connect thecover-plate-moving mechanism between the cover plate and the fork apronadjacent the one fork. The only structural modification required to thetruck is the connection of the lug 46 to the fork apron adjacent therear end of the fork. The conversion apparatus, composed of the coverplate and the ram assembly, may be removed from the truck at will ifdesired. Where a hydraulic ram is used to move the cover plate along thefork member, certain modifications obvious to one skilled in the artmust be made to the hydraulic system of the truck. Alternatively, asupplemental hydraulic system may be attached to the truck.

The above described apparatus is to be distinguished from certain priorart structures such as those disclosed in US. Pat. No. 2,774,498 issuedto Cordes et al. on Dec. l8, 1956, and in U.S. Pat. No. 2,788,909 issuedto Kughler on Apr. 16, i957. Both of these patents disclose devices forextending the length of the forks of a forklift truck to enable thetruck to be used for handling large crates and the like which are toolarge to be held firmly by gravity on forks of standard dimensions. Theydo not disclose apparatus for driving a load along the forks to changethe position of the load relative to the truck.

The present apparatus is also to be distinguished over a structure likethat shown in US. Pat. No. 2,536,068 issued to Lehmann on Jan. 2, 1951.This patent shows movable extensions fitted to each of a pair of forksin a conventional forklift truck. The extensions are movable along theforks by hydraulic rams. The Lehmann rams, however, operate in unisonand cannot be operated independently of one another. There is nodisclosure that the angular relation between the load and the truck bealtered. Accordingly, such a device such as that shown in the Lehmannpatent is like those structures shown by Cordes et al. and Kughler inthat the extensions merely increase the capability of the truck forhandling large cartons and the like.

Although specific structure has been shown and described in theforegoing explanation of a preferred embodiment of the invention, thishas been by way of example only and is not to be considered as limitingthe scope of the invention.

lclaim:

1. Attachment apparatus for a forklift truck having a verti callymovable fork apron carrying a pair of substantially identical spacedhorizontal fork members adapted to support a load, the apparatuscomprising an elongated cover member for enclosing one of the forkmembers, the cover member having a length as long as the horizontallength of the one fork member, the cover member having an open end and aclosed end for enclosing the tip of the one fork member, means formounting the cover member to the one fork member independently of theother fork member for movement of the cover member along the uppersurface of the one fork member toward and away from the fork apron,means carried by the cover member operable for moving the cover memberalong the one fork member independently of the other fork member, and askeg secured to the underside of the one fork member adjacent the forkapron and having a lower surface including a first portion faired intothe surface of the one fork member adjacent the apron and a secondportion substantially coplanar with the undersurface of the covermember.

2. Apparatus according to claim 1 wherein each fork member has avertical leg mounted to the fork apron and a horizontal leg extendingforwardly of the truck from the apron, the cover member enclosing thehorizontal leg of the one fork member, the cover member has sideextensions which, when the cover member moving means is in a normal atrest condition thereof with the open end of the cover member spaced fromthe vertical leg of the one fork member, extend on opposite sides ofsaid vertical leg, the extensions having upper surfaces disposedsubstantially in the plane of the top of the cover member.

3. In a forklift truck having a vertically movable carriage including anapron and a pair of spaced lifting fork members, said fork memberssupporting respective portions of a load engaged therewith and extendedin a cantilevered fashion forwardly of the truck from the apron tounsupported tip ends spaced from the apron, apparatus comprising anelongated cover member supported by one of the fork memberssubstantially enclosing the one fork member from its unsupported end toadjacent its supported end, the cover member having a closed endenclosing the tip end of the one fork member and an open end disposedadjacent to and forwardly of the apron, the cover member including aportion disposed over and aligned with the length of the one fork memberfor engaging the adjacent portion of a load supported by the forkmembers, the cover member having guide means cooperating with the onefork member for guiding the cover member in load-bearing movement alongthe length of the one fork member, bearing means mounting the covermember to the one fork member wholly independently of the other forkmember for load-bearing guided movement of the cover member along theone fork member, cover member moving power means connected to the covermember and the carriage operable for moving the cover member along theone fork member to move the portion of a load supported by the covermember relative to the portion of the load supported by the other forkmember to move the load angularly about a vertical axis through theload, and means cooperating between the open end of the cover member andthe supported end of the one fork member for preventing foreign bodiesfrom wedging between the open end of the cover member and the one forkmember sufficiently to hinder movement of the cover member toward theapron in response to operation of the power means.

W i-v F PO-WJO UNITED N r \f CERTIFIQAI I, ()I CQRRILLIION Patent No. 3561 Dated February 197] Inventor(s) Thomas N Melin It is certified that:error appears in the above-identified pace: and that said Letters Patentare hereby corrected as shown below:

Column 2, line 40, after "engage" delete -of--;

line 63, for "shows" read -shown--.

Coluinn 3, line 35, for "lug 46" read --che ram pistc lug--' I line 36,after "desired," read -as shown in 4, o

Signed and sealed this 21st day of September 1971.

(SEAL) Attest:

EDWARD M-FLETCHERJR- ROBERT GOTTSCHALK Attesting Officer ActingCommissioner of Pa

1. Attachment apparatus for a forklift truck having a vertically movablefork apron carrying a pair of substantially identical spaced horizontalfork members adapted to support a load, the apparatus comprising anelongated cover member for enclosing one of the fork members, the covermember having a length as long as the horizontal length of the one forkmember, the cover member having an open end and a closed end forenclosing the tip of the one fork member, means for mounting the covermember to the one fork member independently of the other fork member formovement of the cover member along the upper surface of the one forkmember toward and away from the fork apron, means carried by the covermember operable for moving the cover member along the one fork memberindependently of the other fork member, and a skeg secured to theunderside of the one fork member adjacent the fork apron and having alower surface including a first portion faired into the surface of theone fork member adjacent the apron and a second portion substantiallycoplanar with the undersurface of the cover member.
 2. Apparatusaccording to claim 1 wherein each fork member has a vertical leg mountedto the fork apron and a horizontal leg extending forwardly of the truckfrom the apron, the cover member enclosing the horizontal leg of the onefork member, the cover member has side extensions which, when the covermember moving means is in a normal at rest condition thereof with theopen end of the cover member spaced from the vertical leg of the onefork member, extend on opposite sides of said vertical leg, theextensions having upper surfaces disposed substantially in the Plane ofthe top of the cover member.
 3. In a forklift truck having a verticallymovable carriage including an apron and a pair of spaced lifting forkmembers, said fork members supporting respective portions of a loadengaged therewith and extended in a cantilevered fashion forwardly ofthe truck from the apron to unsupported tip ends spaced from the apron,apparatus comprising an elongated cover member supported by one of thefork members substantially enclosing the one fork member from itsunsupported end to adjacent its supported end, the cover member having aclosed end enclosing the tip end of the one fork member and an open enddisposed adjacent to and forwardly of the apron, the cover memberincluding a portion disposed over and aligned with the length of the onefork member for engaging the adjacent portion of a load supported by thefork members, the cover member having guide means cooperating with theone fork member for guiding the cover member in load-bearing movementalong the length of the one fork member, bearing means mounting thecover member to the one fork member wholly independently of the otherfork member for load-bearing guided movement of the cover member alongthe one fork member, cover member moving power means connected to thecover member and the carriage operable for moving the cover member alongthe one fork member to move the portion of a load supported by the covermember relative to the portion of the load supported by the other forkmember to move the load angularly about a vertical axis through theload, and means cooperating between the open end of the cover member andthe supported end of the one fork member for preventing foreign bodiesfrom wedging between the open end of the cover member and the one forkmember sufficiently to hinder movement of the cover member toward theapron in response to operation of the power means.